/*
 *  Copyright (c) 2001 Sun Microsystems, Inc.  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *
 *  1. Redistributions of source code must retain the above copyright
 *  notice, this list of conditions and the following disclaimer.
 *
 *  2. Redistributions in binary form must reproduce the above copyright
 *  notice, this list of conditions and the following disclaimer in
 *  the documentation and/or other materials provided with the
 *  distribution.
 *
 *  3. The end-user documentation included with the redistribution,
 *  if any, must include the following acknowledgment:
 *  "This product includes software developed by the
 *  Sun Microsystems, Inc. for Project JXTA."
 *  Alternately, this acknowledgment may appear in the software itself,
 *  if and wherever such third-party acknowledgments normally appear.
 *
 *  4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA" must
 *  not be used to endorse or promote products derived from this
 *  software without prior written permission. For written
 *  permission, please contact Project JXTA at http://www.jxta.org.
 *
 *  5. Products derived from this software may not be called "JXTA",
 *  nor may "JXTA" appear in their name, without prior written
 *  permission of Sun.
 *
 *  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 *  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 *  DISCLAIMED.  IN NO EVENT SHALL SUN MICROSYSTEMS OR
 *  ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 *  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 *  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 *  USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 *  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 *  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 *  OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 *  SUCH DAMAGE.
 *  ====================================================================
 *
 *  This software consists of voluntary contributions made by many
 *  individuals on behalf of Project JXTA.  For more
 *  information on Project JXTA, please see
 *  <http://www.jxta.org/>.
 *
 *  This license is based on the BSD license adopted by the Apache Foundation.
 *
 *  $Id: JxtaHash.java,v 1.1 2005/05/11 03:59:18 hamada Exp $
 */
package net.jxta.impl.util;

import java.util.*;
import java.io.File;
import java.math.BigInteger;
import java.io.InputStream;
import java.io.IOException;
import java.io.ByteArrayInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import org.apache.log4j.Logger;
import org.apache.log4j.Level;

/**
 *  A message digest wrapper to provide hashing using java.security.MesssageDigest
 */
public class JxtaHash {
	private final static Logger LOG = Logger.getLogger(JxtaHash.class.getName());
	public final static String SHA = "SHA";
	public final static String SHA1 = "SHA1";
	public final static String MD2 = "MD2";
	public final static String MD5 = "MD5";
	public final static String DSA = "DSA";
	public final static String RSA = "RSA";
	public final static String SHA1withDSA = "SHA1withDSA";
	private MessageDigest dig = null;

	/**
	 * Default JxtaHash constructor, with the default algorithm SHA1
	 *
	 */
	public JxtaHash() {
		try {
			dig = MessageDigest.getInstance(SHA1);
		} catch (NoSuchAlgorithmException ex) {
			if (LOG.isEnabledFor(Level.DEBUG)) {
				LOG.debug(ex);
			}
		}
	}

	/**
	 * Default JxtaHash constructor, with the default algorithm SHA1
	 *
	 * @param  expression  message to hash
	 */
	public JxtaHash(String expression) {
		this(SHA1, expression);
	}


	/**
	 * Constructor for the JxtaHash object
	 *
	 * @param  algorithm   algorithm - the name of the algorithm requested
	 * @param  expression  expression to digest
	 */
	public JxtaHash(String algorithm, String expression) {
		
		this(algorithm, expression.getBytes());
	}
	/**
	 * Constructor for the JxtaHash object
	 *
	 * @param  algorithm   algorithm - the name of the algorithm requested
	 * @param  expression  expression to digest
	 */
	public JxtaHash(String algorithm, byte [] expression) {
		try {
			dig = MessageDigest.getInstance(algorithm);
			if (expression != null) {
				dig.update(expression);
			}
		} catch (NoSuchAlgorithmException ex) {
			if (LOG.isEnabledFor(Level.DEBUG)) {
				LOG.debug(ex);
			}
		}
	}

	/**
	 * Constructor for the JxtaHash object
	 *
	 * @param  algorithm   algorithm - the name of the algorithm requested
	 * @param  expression  expression to digest
	 */
	public void update(String expression) {
		if (expression != null) {
			dig.update(expression.getBytes());
		}
	}

	/**
	 *  Gets the digest as digestInteger
	 *
	 * @return    The digestInteger value
	 */
	public BigInteger getDigestInteger() {

		return new BigInteger(dig.digest());
	}


	/**
	 *  Gets the digest as digestInteger
	 *
	 * @param  expression  expression to digest
	 * @return             The digestInteger value
	 */
	public BigInteger getDigestInteger(byte [] expression ) {
		dig.reset();
		dig.update(expression);
		return new BigInteger(dig.digest());
	}

	/**
	 *  Gets the digest as digestInteger
	 *
	 * @param  expression  expression to digest
	 * @return             The digestInteger value
	 */
	public BigInteger getDigestInteger(String expression) {

		return getDigestInteger(expression.getBytes());
	}

	/**
	 *   Returns a int whose value is (getDigestInteger mod m).
	 *
	 * @param  m  the modulus.
	 * @return    (getDigestInteger mod m).
	 */
	public int mod(long m) {
		BigInteger bi = getDigestInteger();
		BigInteger mod = new BigInteger(longToBytes(m));
		BigInteger result = bi.mod(mod);
		return result.intValue();
	}


	/**
	 *  convert a long into the byte array
	 *
	 * @param  value  long value to convert
	 * @return        byte array
	 */
	private byte[] longToBytes(long value) {
		byte[] bytes = new byte[8];
		for (int eachByte = 0; eachByte < 8; eachByte++) {
			bytes[eachByte] = (byte) (value >> ((7 - eachByte) * 8L));
		}
		return bytes;
	}

}

